This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The high prevalence of breast cancer calls for safe and effective chemoprevention. Promising anti-breast cancer effects have been observed from an ethanol/water extract from bamboo, Phyllostachys edulis, one of the most widely distributed and fastest growing plants. The bamboo extract (BEX) as a dietary supplement reduced the incidence of mammary tumors in 7,12-dimethylbenz[a]anthracene (DMBA)-treated lean Sprague-Dawley (SD) rats by 44%, enhanced tumor tissue differentiation, and up-regulated the activity of estrogen-conjugating hepatic sulfotransferases by 63% (P=0.011). BEX also reduced the tumor weight in obese SD rats by 68% (P=0.023). Moreover, BEX inhibited the proliferation of estrogen receptor (ER)-positive human breast cancer cells, possibly through relieving oxidative stress and inducing cellular senescence. Thus multiple pathways may contribute to the anti-breast cancer function of BEX, such as enhancing estrogen metabolism;accelerating the differentiation of mammary gland;ameliorating oxidative stress;inducing senescence in breast cancer cells;and inhibiting the acceleration of tumor growth in obese subjects. This investigation will focus on: (i) The influence of BEX on DMBA-induced mammary tumors, including using magnetic resonance imaging (MRI) to monitor the development of micro-tumors, characterizing the molecular properties of both micro- and grown tumors, and studying tissue invasion and metastasis of the tumors. (ii) The influence of BEX on the differentiation of mammary gland and estrogen metabolism in the liver. (iii) The toxicity of BEX in SD rats as a dietary supplement. The new knowledge obtained from this study will lay a firm basis for characterization of the potentially novel anti-breast cancer compound(s) in BEX.